Atom Economy Calculator
Measure how efficiently a reaction uses atoms.
Results update as you type.
How it works
Atom economy measures how much of the reactant material actually ends up in the desired product, and this calculator computes it — a core idea in green chemistry. You enter the molar mass of the product you want and the total molar mass of all the reactants, and it returns the percentage atom economy. The calculation divides the product's molar mass by the combined molar mass of the reactants and multiplies by 100. A high atom economy means most of the atoms from the reactants become useful product, with little turned into waste or unwanted by-products; a low atom economy means much of the starting material is discarded. Unlike percent yield, which measures how much product you actually obtained versus the theoretical maximum, atom economy is a property of the reaction equation itself and reflects inherent efficiency regardless of how well the reaction is run. Addition reactions, where reactants combine into a single product, have 100 percent atom economy, while substitution and elimination reactions that produce by-products have lower values. Chemists favor high-atom-economy routes to reduce waste, cost, and environmental impact. Enter the product and total reactant molar masses to find the atom economy.
Atom economy = (product molar mass ÷ total reactant molar mass) × 100
Atom economy is the molar mass of the desired product divided by the sum of the molar masses of all reactants, multiplied by 100. It shows the percentage of reactant mass that ends up in the useful product rather than in waste or by-products, a key green-chemistry efficiency measure.
Source:Green chemistry principles
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter desired product molar mass and total reactant molar mass.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Atom economy updates instantly as you type — no button to press.
Frequently asked questions
What is atom economy?
Atom economy is a measure of how efficiently a reaction uses its reactant atoms, calculated as the molar mass of the desired product divided by the total molar mass of all reactants, times 100. A high value means most reactant mass becomes useful product; a low value means much becomes waste. It is a key green-chemistry concept.
How is atom economy different from percent yield?
Atom economy is a theoretical property of the balanced equation, showing what fraction of reactant mass could become product even under perfect conditions. Percent yield measures how much product you actually got compared to the theoretical maximum in a real experiment. A reaction can have high atom economy but low yield, or vice versa; both matter for efficiency.
Which reactions have 100 percent atom economy?
Addition reactions, in which two or more reactants combine into a single product with no by-products, have 100 percent atom economy because every reactant atom ends up in the product. Reactions that produce additional by-products, such as substitution, elimination, or condensation reactions, have lower atom economy because some atoms leave in the unwanted products.
Why does atom economy matter?
High atom economy means less waste, lower raw-material costs, and reduced environmental impact, since fewer atoms are discarded as by-products. It is a central principle of green chemistry, guiding chemists to design or choose reaction routes that convert as much starting material as possible into the desired product rather than into waste that must be treated or disposed of.
How do I calculate the total reactant molar mass?
Add the molar masses of all reactants, each multiplied by its coefficient in the balanced equation, so every atom entering the reaction is counted. Use this sum as the denominator. The numerator is the molar mass of just the desired product. Balancing the equation correctly first is essential for an accurate atom economy result.